Vibratory impact device



March 3, 1970 TATSUO OGURA 3,498,334

VIBRATORY IMPACT DEVICE Filed Nov. 8, 1.966 5 Sheets-Sheet 1 FIG. 2

7/17/14 Kl M2 March 3, 1970 Y TATSUO OGURA 3,498,334

VIBRATQRY IMPACT DEVICE Filed Nov. 8. 1966 5 Sheets-Sheet z March 3, 1970 TATSUO OGURA 3,493,334

vxsrmwoav IMPACT nsvxcn Filed Nov. 8, 1966 5 Sheets-Sheet s March 3, 1970 TATSUO OGURA VIBRATORY IMYACT DEVICE 5 Sheets-Sheet 4 Filed Nov. 8. 1966 March 1970 TATSUO OGURA 3,493,384

VIBRATORY IMPACT DEVICE Filed Nov. 8. 1966 5 Sheets-Sheet 5 FIG. 13

United States Patent 3,498,384 VIBRATORY IMPACT DEVICE Tatsuo Ogura, Icikawa, Japan, assignor to Chyugoku Kogyo Kabushiki Kaisha, Hiroshima City, Japan, a corporation of Japan Filed Nov. 8, 1966, Ser. No. 592,925 Int. Cl. E0241 3/04; E01c 19/38; F16h 33/20 US. Cl. 172-40 1 Claim ABSTRACT OF THE DISCLOSURE A vibratory impact device having two degrees of freedom in which a vibratory body and a resonating member with an integral impacting member are mounted on a base and two groups of respective springs are mounted between the base and the vibrating body and the resonating member whereby the output of the impacting member may be substantially increased due to the resonance, while the amplitude of vibration of the vibrating body may be kept close to zero by regulation of the spring constants of the Springs.

This invention is related to a vibratory impact device, and more particularly to a vibratory impact device comprising a vibrating system having two degrees of freedom, in which an impacting operation is effected by actuating a vertically vibrating body from a prime mover and by converting the vibration of said body into an impulsive force while transmitting said vibration to a resonating member through a spring means. At the output end of said device there is provided suitable means to work the ground surface.

In conventional earth tamping machines utilizing a vibratory force, such vibratory force has been produced in a vibrating system having only one degree of freedom and transmitted to the earth indirectly through a spring means, in most cases. In some earth tamping machines, the vibratory force is transmitted directly to the earth without using a spring means.

Heretofore however, there have been no earth tamping machine to tamp the earth by utilizing the vibrating force directly as an impact force for the tamping. One of the most important reasons therefor is the fact that a vibratory body of such a tamping machine can be damaged by the reaction of the earth to the impact, which can lead to various difficulties including injury to the operator thereof. Moreover, it is necessary to provide the amplitude of the vibration or the magnitude of the vibratory impact force in a selectively variable manner over a wide range, in order to meet various needs of different earth conditions and different kinds of soil. It has been believed to be too expensive to meet such variable needs in a single vibrating tamping machine, because the efficiency thereof is too low to make it economical.

It is a principal object of the present invention to obviate the aforementioned difficultie's in conventional earth tamping machines by providing a new vibrating impact device comprising a vibrating system having two degrees of freedom, which will be described in detail hereinafter.

Another object of the present invention is to provide a construction working tool device based on resonance phenomenon, which comprises a vibrating means and a tool member to be fixed on the out-put end thereof and to be in resonance with said vibrating means, said tool member being used for breaking up or wrecking a paved road surface or for tamping earth surface. In a preferred embodiment of the invention, a resonating body is supported on a body of the device by means of a pneumatic spring having a variable spring constant, and a vibrating means is held on the resonating body whose mass can be regulated in such a manner that the resonating body can be kept in resonance with the vibrating frequency of the vibrating means without changing the amplitude of the vibration thereof, thereby the device can be utilized most efficiently to carry out duties assigned thereto.

Another object of the invention is to provide a vibrating impact device capable of obviating shortcomings of conventional earth tamping machines or road roller. With an impact device according to the invention, it is possible to regulate readily the internal pressure of the pneumatic spring when the stamping vibration is disturbed by variation of the elasticity of the earth to be tamped so that the vibrating impact device can be used for dealing with a number of different earth conditions, whereby efficient earth tamping operation can be conducted safely and economically.

A further object of the invention is to provide a resonant type earth tamping device having a spring means to be resonated. In a preferred embodiment of the invention, the impulsive reaction of the tamping operation is not transmitted back to a vibrating body having a prime mover, to actuate, it nonetheless a tamping force of several times as large as the vibrating force of the prime mover, can be obtained, whereby the tamping operation can be conducted very efficiently, and in addition, the tamping machine can be made in a compact form for a certain desired tamping force as compared with that of conventional tamping machines for the same tamping force. Thus, the tamping machine based on the vibrating impact device of the invention can be transported easily, and the construction of the tamping machine can be made so simple that the chance of mechanical or physical break down of the machine is considerably reduced, which serves to improve the safety of the operator handling the machine.

Another object of the invention is to provide a vibrating impact type of earth tamping machine having a means for regulating a spring constant of a pair of pneumatic spring means disposed on both sides of an intermediate impact plate by feeding or discharging fluid into and out of such pneumatic spring means. Thus, it is made possible to obtain a tamping ratio of several to over ten times with a device of the invention, and at the same time mechanical shocks of impact operation on the tamping device can be substantially eliminated so as to ensure a long service life of the device Without causing any damage thereon, whereby the safety of the operator of the device can be greatly improved.

Still another object of the invention is to provide a resonant impact type earth tamping machine having a means for converting a vibrating force into an impact force to tamp the earth directly, in which the chance of the breakage of a vibrating body of the machine due to the reaction against the impact of tamping operation is eliminated by using the principleof resonance of a spring means. In a preferred embodiment of the invention, a vibrating force is amplified by taking advantage of the resonance phenomenon to tamp the earth directly, whereby providing tamping effects several to twenty times better than those of conventional tamping machines, while substantially eliminating the chance of breakage of the machine caused by the tamping operation over a long period of time.

A further object of the invention is to provide an improved tool device driven by a vibratory power source, in which vertical vibration of a vibrating means mounted on the tool device is used to actuate a resonating body in resonance with the vertical vibration so as to tamp or break-up the earth with a tool secured to the vibrating tion,-it-is made possible-to-vibrate a vibrating-body and a resonating body thereof in a vertical direction while eliminating the horizontal component thereof, so as to cause efficient resonance of the resonating body for improving the efficiency in the tamping operation. At the same time, it is made possible to damp the vibration of the aforementioned vibrating body in a variable manner in. order toselect a proper vibrating amplitude of the resonating body upon resonance for eliminating the danger of the breakage of the entire tool device.

The above and other objects and characteristic features of the present invention will become evident and will be more readily understood from the following description taken in conjunction with the accompanying drawings, in which:

FIGS. 1 and 2 are diagrammatic illustrations :of operative principles of a device according to the present invention, shown asapplied to two different vibrating systems respectively;

FIG. 3 is a graph useful in describing the operative principles of the device of the invention;

FIG. 4 is a diagrammatic illustration, partly in section, of an embodiment of the device according to the invention, adapted for wrecking a paved road surface;

FIG. 5 is a diagrammatic illustration of the piping system of the device shown in FIG. 4;

FIG. 6 is a side view of an earth tamping machine according to the invention with a part thereof being broken away and shown in dash-dot lines;

FIGS. 7 and 8 are respectively a side elevation and a bottom view of another embodiment of the invention similar to the earth tamping machine of FIG. 6, certain parts being broken away in FIG. 7 and appearing in section, one half of FIG. 8 being in transverse section;

FIGS. 9 and 10 are respectively a side elevation and a plan view of a further modification of the machine shown in FIG. 6, certain parts being broken away and appearing in section in FIG. 9;

FIGS. 11 and 12 are respectively a side elevation and a partial plan view of another earth tamping machine according to the invention, certain parts in FIG. 11 being broken away and appearing in section;

FIG. 13 is a fragmental side view, illustrating a mod ification of a part of the machine shown in FIGS. 11 and 12; and

FIGS. 14 and 15 are respectively a side elevation and a plan view of a device similar to the earth tamping machine shown in FIG. 6, certain parts of FIG. 14 being broken away and appearing in section.

The same parts or elements are designated by the same reference numerals and symbols throughout the drawings.

Referring to FIG. 1 illustrating operative principles of the vibrating impact device of the present invention, a body M of mass m is supported by spring means K having a spring constant k secured on a base B, and another body M of mass m is retained by spring means K having a spring constant k secured on the body M The assembly of the aforementioned bodies, spring means and the base is to constitute a vibrating system having two degrees of freedom, provided that the base B is a stationary rigid body. In such vibrating system, when the body M is vibrated by a certain driving means V, then it is possible to bring the body M into resonance with vibration of'the body M by selectively adjusting the spring constants k k of the 'spring means K K FIG. 2 shows a similar vibrating system having two degrees of freedom similar to that shown in FIG. 1, in which the body M is vibrated in the vertical direction'by means of the driving means V mounted thereon. vThe bodies M1 and M will be brought similarly into the resonant condition depending on suitably selecting the spring constants k and k but the mode thereof is to be naturally different from tothose skilledinthis'fieldf" i that of FIG. 1, as is obvious The devices according to the present invention intend to utilize these two types of vibrating systems. The variations of the amplitudes in these systems are illustrated in the diagram of FIG. 3 which has been drawn up by analyzingmotion Equations 1 and 2 to be given hereinafter. At this point it should be recalled that the vibrations in these systems'are vertical [or have a directionality of one direction.

In FIG. 1,;the equations of motion are:

wherein:

P represents the maximum value of a.driving force; to represents the angular frequency of the driving force, given by 21rn, n being the number of revolutions per unit time of a shaft; to transmit the driving force;

- P sin to! represents the magnitude of the driving force at time t, provided that the driving force is zero when time is zero;

x x represent displacements of the bodies M and M respectively; and

m m represent masses of the bodies M and M, re spectively.

If it is assumed that X =a sin wt, X22612 sin wt wherein a and a respectively represent amplitude of the bodies M and M then one obtains the following relation.

. & =-a w sin wt, zil' =a (0 sin wt Upon substitution of the formulae respectively into Formulae 1 and 2, the following are obtained;

Upon substitution of the following in order to simplify the Formulae 3 and 4, the following equations are ob tained;

and

In order to establish the condition, a 0, the follow- In order to establish the condition, a :0, the following must be established;

and so From Formula 15 a :P k (17) It is apparent from the foregoing description that when the body M is actuated by a driving force represented by P with the angular frequency w, the amplitude a of the vibrating movement of the body M will not actually come down to zero, but it is very small to keep the body M approximately in a stationary condition, while effecting the vibration of the body M with an amplitude Of a Spring means having constant and invariable spring constants, such as metallic coiled spring, are not suitable for the device of the invention, because with such springs means, it not possible at all to follow up the variation of the angular frequency w of the driving force and to vary the resonant amplitude a of the vibration of the resonating body M Accordingly, in the device of the invention, springs means having a variable spring constant, such as pneumatic springs whose spring constants can be varied by regulating the internal volumes thereof or pneumatic pressure therein, are utilized to support the vibrating body and resonating body. Furthermore, in a preferred embodiment of the invention, it is also permissible to fill the resonating body M with liquid or gas so that the amount of said fluid may be controlled, whereby the mass m of the body M can be varied for operating the vibrating impact device most efficiently by realizing the best resonance conditions according to the aforementioned relations represented by Formulae l, 2, etc.

In an embodiment of the invention shown in FIG. 4, which is useable for breaking-up or wrecking a paved road surface, a vertically movable vibrating body 1 is actuated by a prime mover 2, such as an electric motor, an internal combustion engine, and the like. The rotation of the prime mover 2 is converted into the vertical reciprocative movement of the vibrating body 1 by a suitable means (not shown), which is well known to those skilled in the art, for instance a crank mechanism.

The vertical vibration of the body 1 thus produced is transmitted to a resonating body 4 through pneumatic springs 3 and further to a wheeled base or frame 6 through further pneumatic springs In this particular embodiment of the invention, the vibrating body 1 is secured on a square holding plate 7 which is in turn supported by the resonating body 4 by means of four pneumatic springs 3 located at the four corners of the square holding plate 7 and the resonating body itself is also made square to receive lower ends of said pneumatic springs 3 The square resonating body 4 is in turn supported by the base 6 through four pneumatic springs 5 mounted at the lower side surface of the resonating body 4 at four corners thereof by suitable fastening means. The lower ends 9 of the pneumatic springs 5 are secured to the recessed portion of the base 6, as illustrated in FIG. 4. When air under pressure is fed into the pneumatic springs 3 and 5 by means of an air compressor (not shown) and the air pressure in those air springs are so increased as to provide spring constants k and k respectively, as defined in the foregoing with reference to Formulae 1 and 2, then the resonating body 4 is substantially in resonance with the vibration of the vibrating body 1, provided that the angular frequency of the driving force applied to the body 1 by the prime mover 2 is P as defined by the formula in the proximity of the resonating frequency of the vibrating system. An arm including a lower plate 9 having spikes 10 planted thereon is affixed to the resonating plate 4, so that the spikes 10 act to wreck the paved road surface responsive to the vibration of the body '4 in resonance with the vibrating body 1.

According to the invention, the spring means 3 and 5 are not limited to pneumatic springs, but any spring means having variable spring constants can be used. For instance, fluid springs to be actuated by a fluid other than air can be utilized, and in this case, the aforementioned air compressor should be replaced with a suitable means to pressurize the fluid to be filled in the fluid springs.

Generally speaking it is necessary to vary the amplitude of the vibration of the resonating body 4 to meet variation of the road surface conditions responsive to the progress of wrecking operation or due to the movement of the impact device. It is possible to change the frequency and the amplitude of the vibration of the resonating body 4 by regulating the spring constant of the fluid springs or air springs by controlling the fluid pressure thereof. With the variation of the fluid pressure alone, however, the conditions for resonace derived from the Equations 1 and 2 are lost and the efficiency of the impact machine is reduced. Therefore, it is necessary to modify the mass of the resonating body 4 together with the spring constants of the spring means connected thereto for maintaining the body 4 in resonace with the vibration of the vibrating body 1. In this particular embodiment of the invention, the resonating body 4 is provided with a hollow chamber, so that the mass of the body 4 can be regulated by feeding or discharging suitable liquid therein and therefrom.

In FIG. 4, a pipe 11 is provided for feeding the liquid into the body 4, and an air pipe 12 is provided to control the air pressure in the air springs 3 and 5 as well as in the hollow chamber of the body 4.

FIG. 5 shows a diagram illustrating piping systems for regulating the air pressure in the air springs 5 as well as for controlling the mass of the resonating body 4. For simplicity, the air springs 3 are not shown in FIG. 5, but it is apparent to those skilled in the art that such air springs can be placed between the vibrating body 1 and the resonating body 4 and can be controlled in the same manner as air springs 5 There are provided a water tank 13 to store Water to be delivered to the air springs 3 and 5 and another liquid tank 14 to store comparatively heavy liquid, such as a mixture of water, clay, and bentonite, which tanks 13 and 14 are both kept at an elevated pressure by feeding high pressure air therein from an air compressor 15. T o discharge air from the air springs 5 a valve 16 is opened to feed Water into the air springs and at the same time the cross valves 17 are actuated to allow air escape therethrough, To feed the comparatively heavy liquid into the inside chamber of the resonating body 4, a valve 18 is opened and at the same time a cross valve 19 is actuated to allow air escape therethrough.

To feed air into the air springs for modifying the spring constants thereof, cross valves 17 are so actuated as to allow compressed air passing from the air compressor 15 to the air springs therethrough, and at the same time a valve 20 is opened to release the pressure of the water tank 13 for allowing return flow of water from the air springs 5 back to the water tank 13. To remove the comparatively heavy liquid from the inside chamber of the resonating body 4 for reducing the mass thereof, the cross valve 19 is so actuated as to feed air under pressure from the air compressor 15 into the inside chamber of the body 4, and at the same time another cross valve 21 is actuated to release air from the tank 14 to reduce the pressure therein, whereby upon opening of the valve 18, the comparatively heavy liquid in the inside chamber of the body 4 is forced to flow back to the tank 14. A valve 22 is inserted in series with the cross valve 21 between the two tanks 13 and 14, as illustrated in FIG. 5, and the valve 22 cooperates with the cross valve 21 in controlling the liquid floW and in maintaining the constant air pressure for keeping the flow rate of the liquids at a cer tain predetermined level. The valves 21 and 22 can be also used as safety valves. It is preferable to install all valves at a centralized control board or chamber in order to facilitate well coordinated operation of the impact means.

In the aforementioned mathematical treatment of the vibrating system with reference Formulae 1 to 8, it is assumed that there is no loss in the system. However, there are actually various deviations from such assump tions and conclusions based on such assumptions, for instance the amplitude of the vibrating movement of the vibrating body 1 is sometimes increased excessively, or the vibrating system is moved in a horizontal direction due to certain reasons to cause abnormal vertical vibration of the resonating body 4, or the amplitude of the reciprocative vertical movement of the resonating body 4 is diminished due to losses in the vibrating system. According to the present invention, in order to prevent such difficulties, the movement of the resonating body 4 is guided by rollers 23 having very small coefficients of friction disposed along four sides of the body 4 for keeping the movement of the body 4 along the vertical direction with the rolling contact between the rollers 23 and the body 4. Furthermore, the support plate 7 of the vibrating body 1 is provided with projections 24 extending from four sides thereof in such a manner that the projections 24 are slidably engaged with guide members 25 secured to the base 6 of the impact device. Thus, any irregular vibration of the vibrating body 1 in the hori zontal direction is rapidly attenuated by the loss at the sliding contact between the members 24 and 25.

With the embodiment shown in FIG. 4, it is permissible to remove the tool or spikes 10 provided on the bottom surface of the lower plate 9 of the resonating body 4 for using the impact device as a tamping machine to tamp the earth with the flat surface of the lower plate 9.

FIG. 6 illustrates an embodiment of the vibrating impact device of the invention, usable as an earth tamping machine, in which a resonating body 4, which is also used as a tamping member, is suspended from the support plate 7 and a pneumatic spring is inserted between the resonating body 4 and the support plate 7 at about the center thereof While securing the upper and lower ends thereof to the plate 7 and the body 4 respectively by suitable securing means, such as bolts and nuts. A plurality of metallic spring members 26 are similarly inserted between the support plate 7 and the resonating body 4 so as to surround the pneumatic spring 5 while securing the upper and lower ends thereof to the plate 7 and the body 4 respectively in the manner similar to the pneumatic spring 5 The support plate 7 is supported on base B by a plurality of pneumatic spring means 3 and spaced from the surface of the ground tobe tamped, as illustrated in the figure.

With the impact device shown in FIG. 6, when suitable fluid is fed into the pneumatic spring means 5 the spring means 5 are elongated together with the metallic spring means 26 until the tamping member 4 reaches the ground surface. Then, the pneumatic spring means 3 holding the support plate 7 are fed with suitable fluid in a similar manner to the pneumatic spring means 5 for providing proper spacing between the ground surface and the tamping member 4.

Mathematically speaking, if equations of motion of the vibrating system of FIG. 6 is worked out to find relations between the frequency of vibration of the tamping member 4, the mass of the same, and various spring constants related thereto, then it is apparent that the spring constant of the pneumatic springs 3 holding the support plate 7 does not afford such relations at all. Therefore, the only spring constants usable for controlling the vibration of the tamping member 4 are those of the metallic spring members 26 and the pneumatic spring 5 located at the center of the metallic springs.

In operation of the vibrating impact device of FIG. 6, upon actuation of a prime mover 2 incorporated with a converting means (not shown) to convert rotation into a vertical reciprocative movement, the vibrating body 1 is vibrated together with the support plate 7 Then as the pneumatic spring is filled with suitable fluid at a certain pressure, the resonating body or the tamping member 4 is vibrated at an amplitude a which is determined by a composite spring constant including the effects of the metallic springs 26 and the pneumatic spring 5 from a curve as shown in FIG. 3. Thus, the tamping member 4 can be vibrated at a large amplitude to tamp the ground effectively while keeping the vibrating body 1 substantially stationary in the same manner as that described hereinbefore referring to FIGS. 4 and 5. As the vibrating impact device is transferred from position to position, for instance by means of a suitable transferring means, a certain area of ground can be tamped uniformly and effectively.

FIGS. 7 and 8 illustrate another embodiment of the vibrating impact device according to the present invention, in which metallic coiled springs are used instead of pneumatic springs in the proceeding embodiments. A vibrating body 1 having a prime mover 2 mounted thereon and a resonating body 33 are slidably supported by upright support studs 35 secured at four corners of a base plate 34. A coiled spring 36 is inserted between the vibrating body 1 and the resonating body 33, and another coiled spring 37 is inserted between the resonating body 33 and the base plate 34. The upper and lower ends of the coiled spring 36 are secured respectively to a spring seat 1' affixed to the lower surface of the vibrating body 1 and to another spring seat 33' embedded on the upper surface of the resonating plate 33, by means of a suitable securing means, such as welding. Similarly, the upper and lower ends of the coiled spring 37 are secured respectively to a spring seat 33" embedded on the lower surface of the resonating body 33 and to another spring seat 34' embedded in the base plate 34. Each of said spring seats 1', 33, 33", and 34' is disk shaped. There are provided leg means 38 to settle the impact device on the ground while spacing the base plate 34 from the ground surface. A stem 39 extends from the central portion of the lower surface of the resonating body through the base plate 34 while allowing substantially wide spacing between the resonating body 33 and the base plate 34. The lower end of the stem 39 is so adapted as to receive a tamping plate 40 with a proper distance from the ground surface, in a replaceable manner with a wrecking plate having a plurality of spikes. A top plate 41 is secured to the top ends of the studs 35 by a suitable fastening means, such as bolts and nuts, and a lug 43 having an eye opening 42 is secured to the top plate to facilitate transportation of the impact device, e.g. by a crane.

In operation of the impact device shown in FIGS. 7 and 8, upon actuation of the prime mover 2, the vibrating body is forced to vibrate in the vertical direction to transmit the amplitude and the frequency of the vibration to the resonating body 33 through the coil spring 36 for effecting vibration of the resonating body 33. The intrinsic spring constants of the coil springs 36 and 37 and the natural frequencies of the same can be so selected that, the relations among such constants, the amplitude and angular frequency of the external actuating force of the prime mover 2, and masses and displacements of vibrating and resonating bodies 1 and 33 represent characteristics of a vibrating system having two degrees of freedom. Thus, with properly selected constants of springs 36, 37, and masses of bodies 1, 33, the resonating body 33 is substantially in resonance to the vibration of the vibrating body 1, which means a large amplitude of vibration occurring at the resonating body 33 while the amplitude of the vibrating body 1 is kept at a minimum. Consequently, the tamping plate 40 secured to the stem 39 acts to tamp the ground effectively.

According to experiments, with a driving force of 3 tons applied to the vibrating impact device of the invention at a forced frequency of 500 c/m. (cycles per minute), it was possible to obtain an amplitude of 3 mm. in the vibration of the vibrating body while producing an earth tamping force of 40 tons at an amplitude of 40 mm. at the resonated vibration of the resonating body. The impact device used in the above experiment was the type shown in FIGS. 7 and 8, and the reaction to the tamping operation of the tamping plate 40 was absorbed by the coil springs 36 and 37 to substantially eliminate the effects of such reaction on the vibrating body 1 and the actuating means 2 mounted thereon. Furthermore, it was proved in the experiments that the studs 35 served to prevent horizontal vibration from occurring due to fatigue of the coil springs and to damp too large amplitudes of the resonated vibration of the resonating body when the frequency was reduced, thereby the danger of damage of the springs due to excessive elongation thereof corresponding to the excessively large amplitude was eliminated. In order to use the impact de vice of the invention as ShOWn in FIGS. 7 and 8 on a sloped ground surface, it is necessary to overcome the high friction between the resonating body 33 and the studs 35.

To reduce such friction, it is permissible to bore an enlarged hollow portion 44 at each corner of the resonating body 33 along the regular openings to receive the 'studs 35, so that balls 45 may be filled in the hollow space 44 to reduce the friction. The hollow openings 44 are normally covered with suitable lids in a removable manner.

FIGS. 9 and illustrate another embodiment of the vibrating impact device of the invention, in which a base plate 29 is placed on the upper surface of a shipshaped tamping plate 40, and a resonating plate or an impact plate 4 is supported by pneumatic springs 5 on the base plate 29. The resonating plate 4 in turn supports a support plate 7 through pneumatic springs 3 which support plate 7 in turn carries a vibrating body 1 incorporated with a prime mover. Impact bosses 46 and 47 are secured to the base plate 29 and the resonating plate 4 respectively in such a manner that upon actuation of the impact device the boss 46 can strike the cooperating boss 47 to transmit the tamping force from the resonating plate 4 to the tamping plate 40. .Four pneumatic springs 3 and four similar pneumatic springs 5 are positioned at four points spaced from the center of the plates 4, 7 and 29 by the same distance. Water passageways 48 and 49 formed in the support plate 7 and the base plate 29 respectively are communicated with a tank 52 through pipes 50 and 51 having valves 57 inserted therein. The tank 52 is supported on the tamping plate 40 in a shock-proof manner by a metallic spring means 53. An air compressor 54 is mounted on the tamping plate 40 in order to supply compressed air to the tank 52 and the compressor 54 is driven by the prime mover (not shown) to actuate the vibrating body 1 through a flexible shaft 55. A handle 56 is secured to one end of the ship-shaped tamping plate 40 to move the vibrating impact device. A plurality of control valves 57, the degrees of opening of which are manually controllable, are inserted between the tank 52 and the pneumatic springs 3 and 5 for regulating the spring constants thereof.

In operation of the vibrating impact device shown in FIGS. 9 and 10, the tank 52 is filled with water while leaving air in a certain predetermined portion thereof. The spring constants of the pneumatic springs 3 and 5 can be varied by feeding water therein while discharging air therefrom through outlet openings (not shown) thereof, and for instance, by filling up the inside space of a pneumatic spring made of rubber walls or bellows, the spring constant thereof can be made comparable to that of a coiled spring made of steel. Then, the vibrating body 10 1 is actuated, and the water in the tank 52 pressurized by gradually feeding compressed air into pneumatic springs 3 and 5 through pipes 50 and 51 while controlling the flow rate of the water by manipulating the control valves 57 in such a manner that the resonating plate 4 can be brought into resonance with the vibration of the vibrating body 1 thus actuated by adjusting the spring constants of the pneumatic springs 3 and 5 as described in the preceding paragraph. Upon attaining the resonance of the resonating plate 4 with the vibration of the vibrating body 1, the boss 46 secured to the plate 4 is so actuated as to strike the cooperating boss 47 secured on the tamping plate 40 to transfer the vibrating energy of the resonating plate to the tamping plate in impact form for carrying out the earth tamping operating effectively In the aforementioned operation of the impact device, the amplitude of the vibration of the vibrating body 1 can be kept a minimum or substantially zero while causing effective vibration of the resonating plate 4 in resonance with the minimum vibration of the vibrating body 1 by selecting proper spring constants of the pneumatic springs so as to meet the resonance conditions of the aforementioned vibrating system having two degrees of freedom. At the same time, the reaction of the earth responsive to the tamping operation of the tamping plate 40 is effectively absorbed by the pneumatic springs 3 and 5 and are not transmitted to the vibrating body 1 and the prime mover associated therewith.

Moreover, the entire impact device acts to make a very small jump responsive to each tamping action of the tamping plate 40, and accordingly, the impact device can be utilized in any desired direction by applying moderate force manually on the handle 56 in a direction to which the device should be moved. If it is desired to move the device forwards or backwards at a compartively high speed, or to effect such forward or backward movement of the device in an automatic manner, then the axial direction Y-Y of the vibration of the vibrating system can be inclined from the vertical direction either backwards or forwards by an angle 0, or 0 respectively, as illustrated in FIG. 9.

When the solid conditions are varied rapidly, e.g. from soft ground to hard ground or vice versa, the amplitude of the vibration of the resonating plate 4 can be increased excessively responsive to the change in the natural frequency of the ground, which in turn can cause a considerable increase in the amplitude of the vibration of the vibrating body 1 together with the support plate 7 Such excessive increase in the amplitude of the vibration of the resonating plate 4, leading to a considerable increase in the amplitude of the vibration of the body 1 and the plate 7, can be easily suppressed by removing the resonance between the resonating plate 4 and the vibrating body 1 by modifying the spring constants of the pneumatic springs 3 and 5 through manipulation of the control valves 57. It is also permissible to mount the tank 52, the air compressor 54, and control valves 57 on a separate tractor (not shown) to maneuver the vibrating impact device instead of mounting them directly on the tamping plate 40.

FIGS. 11 to 13 illustrate still another embodiment of the vibrating impact device of the present invention, in which a ship-shaped tamping plate 40 is pivotally connected to a stem 8 depending from the central portion of a resonating plate 33, and a support plate 7 holding a vibrating body 1 is secured to the upper ends of coiled springs 36 mounted on the resonating plate 33, which is in turn secured to the top end portions of coiled springs 37 mounted on the central portion of a lower support plate 58. The lower support plate 58 is inserted between pneumatic springs 5 secured on a base plate 59 and cooperating pneumatic springs 3 depending from brackets 68 secured on the base plate 59. As shown in FIG. 12, the resonating plate 33 and the support plate 7 are of substantially square shape of the same size, and coiled springs 36 and 37 are positioned at the four corners of such square plate members. The lower support plate 58 is also square shaped and slightly larger than the resonating plate 33 and the support plate 7. The pneumatic springs 3 and 5 are positioned at the four corners of the lower support plate 58. The stem 8 penetrates through the central portion of the lower support plate 5 8, preferably with suitable clearance therefrom around the periphery of the stem 8, and the tamping plate 40 is loosely fitted in an opening 60 of the base plate 59. There are four or two pairs of other pneumatic springs 61 mounted on each side of the base plate 59, and each pair of pneumatic springs 61 are communicated with each other and with a pneumatic spring 5 located close thereto through 'pipes 62. Each pneumatic spring 61 is placed on a pad 67 secured on the base plate 59, and the spring 61 can be compressed by a hemispherical member 66 held by a rod member 64 screwed on a bracket 63 responsive to rotation of a handle 65 secured atop the rod 64. The natural frequencies of the coiled springs 36 and 37 are so selected as to effect resonance of the resonating plate 33 with the vibrating body 1 in proper relations with the masses and natural frequencies of the body 1 and the plate 33.

In operation of the impact device shown in FIGS. 11 and 12, upon actuation of the vibrating body 1, the resonating plate 33 is in resonance with the vibration of the vibrating body 1 thanks to the natural frequencies of the coiled springs 36 and 37 thus selected, and accordingly the amplitude of the vibration of the resonating plate 33 is increased while keeping the amplitude of the vibration of the vibrating body 1 at a minimum or substantially at zero. Consequently, the tamping plate 40 is forced to tamp the ground surface through the opening 60 with a force obtained by amplifying the vibrating force of the vibrating body 1 by several times. Therefore, the tamping force of the impact device of this particular embodiment of the invention is of at least several times as large as initial vibrating force of the vibrating body 1. Furthermore, the reaction of the earth against the tamping operation of the impact device is completely absorbed by the pneumatic springs 3 and 5 and such reaction is never transmitted to the vibrating body 1 to exert undesirable effects thereon. Thus, the danger of the damage of the impact device due to such reaction can be eliminated completely.

Moreover, by varying the pressure of the pneumatic springs 61 with the threaded bars 64 to modify the internal pressure of the corresponding pneumatic spring 5 the height of the spring 5 can be changed to alter the axial direction of the vibration of the vibrating system, consisting of the vibrating body 1, springs 36, 37 resonating plate 33, and the stern having the tamping plate 40 secured thereto, is inclined. Thereby, as the base plate 59 is raised slightly from the ground surface responsive to each tamping action of the tamping plate 40, the entire impact device is moved to a direction corresponding to the aforementioned inclination of the axial direction of the vibrating system.

FIG. 13 illustrates a slight modification of the device shown in FIGS. 11 and 12. In this particular modification, instead of using a stem 8 having a tamping plate 40, a pair of semi-spherical bosses 69 and 70 are aflixed to the lower surface of the resonating plate 331, and the upper surface of the base plate 59, as shown in the figure. Accordingly, upon vibration of the resonating plate 33 the tamping force is transmitted from the vibrating system of the impact device to the base plate 59 by the direct strike of the boss 70 by the cooperating boss 69, whereby, the desired tamping operation of the ground surface can be accomplished effectively.

FIGS. 14 and show another embodiment of the vibrating impact device of the present invention, in which a resonating plate 33 is secured on the upper ends of coiled springs 37 mounted on base plates 59, and a frame 71 holding a vibrating body 1 is secured to the top ends of other coiled springs 36 mounted on the resonating plate 33 The mechanical constants of the vibrating system,

comprising the vibrating body 1, the coiled springs 36 and 37, and the resonating plate 33 are so selected that, upon application of a vertical vibration with a certain predetermined frequency to the vibrating body 1, the resonating plate 33 may be brought into resonance with such vibration. Consequently, a tamping plate 40' secured to the lower end of a stem 8 depending from the central portion of the resonating plate 33 acts to tamp the ground surface between the base plates 59, 59. This particular embodiment of the invention is characterized in that a plurality of brackets 72 are secured on the base plates 59 in such a manner that vertical side surfaces of the frame 71 and the resonating plate 33 are slidably engaged with the corresponding vertical surfaces of the brackets 72. Thereby the vertical vibration of the vibrating body 1 is clamped, and at the same time the horizontal movement of the resonating plate 33 is effectively prevented. At the top end of each bracket 72, there is provided a regulating screw 73 screwed therein, and a boss 74 mounted at the top end of the regulating screw 73 is slidably fitted into a vertical groove formed on a receiving frame 75 secured to the vertical side surfaces of the frame 71. There are also provided a plurality of brackets 76 mounted on the base plates 59 so as to surround the resonating plate 33, a roller 77 being pivoted to the top end of each of such brackets 76 so as to make slidable contact with one of a number of contact plates 78 mounted on the vertical surface of the Plate 33.

According to this embodiment, the brackets 72 and 76 having slidable contact means are provided to damp the vertical vibration of the vibrating body 1 and to prevent horizontal movement of the resonating plate 33. The reason for providing such slidable contact means is as follows. The aforementioned mathematical treatment of the vibrating system is in fact made on the assumption of non-existence of loss or attenuation, in order to simplify the treatment, and the results of such mathematical treatment may hold in the case of a vibrating system having spring means such as pneumatic springs of which the spring constant may be freely adjusted, since disturbance of the vibration amplitude caused by loss in the mechanical elements of the system can be adjusted, and at the same time the spring constants of such pneumatic springs can be set and maintained at the values determined by the mathematical treatment. On the other hand, if metallic springs are used instead of the pneumatic springs, the spring constants of the metallic springs are usually determined definitely While being manufactured, and the attenuation or energy loss intrinsic to such metallic springs can not be eliminated by any means. In other words, it is impossible to operate the vibrating system under the conditions exactly in agreement with the results of the mathematical treatment, and the mathematical analysis based on the aforementioned assumptions becomes meaningless. The present embodiment serves to compensate for the energy loss by providing an additional means for eliminating such loss, so that the assumptions made in the mathematical treatment or analysis are realized in the practical device by mechanical means.

According to the invention, it is also permissible to provide a bearing means for the frame 71 at the top portion of each bracket 72 while providing another bearing means for the resonating plate 33 at the intermediate portion of the same, instead of using separate brackets 76 for the resonating plate 33 In operation of this particular embodiment of the device of the invention, when the base plates 59 are placed on a horizontal ground surface to actuate the vibrating body 1, the springs 36, 37 and the resonating plate 33 are actuated together with the frame 71, and the horizontal component of the movement of the frame 71 and the resonating plate 33 are completely restricted by the 13 slidable engagement between the boss 74 and the receiving member 75 and the similar engagement between the roller 77 and the contact plate 78, for effecting a pure vertical vibration of the resonating plate 33 to ensure satisfactory impacting operation of the device.

Furthermore, when the amplitude of the vibration of the vibrating body 1 is increased excessively to too soft soil or irregular conditions of the prime mover to actuate the vibrating body, the regulating screws 73 can be turned to adjust the clearance between the boss 74 and the receiving member 75 so as to control the friction of the sliding surface between them until suitable amplitude of vibration is obtained.

Moreover, when the impact device is used on a sloped surface, the friction at boss 74, which is lowered from a corresponding position for operation on fiat ground surface, is increased to prevent any movement of the frame 71 or to provide a considerable disturbance to the operation of the vibrating system. To overcome such difiiculties, it is permissible to replace the upper portion of the bracket 72 having said boss 74 with a corresponding upper portion having a roller pivoted thereto, and at the same time to replace the receiving member 75 on the frame 71 with a suitable contact plate, so that the friction may be reduced by using the roller contact. Therefore, it is preferable in this particular embodiment to make the upper portion of the bracket 72 exchangeable.

Though the invention has been described with reference to the embodiments as illustrated in the drawings, various modifications may of course be made without departing from the spirit of the invention.

What is claimed is:

1. A vibrating impact device having two degrees of freedom comprising a vibrating body adapted to be actuated by a prime mover mounted thereon, a resonating member having an impacting member integral therewith, a base member supporting all of the other elements of the device thereon, a first group of spring means between said vibrating body and said resonating member including a metallic spring member and a pneumatic spring having a variable spring constant which is adjusted in relation to the metallic spring member whereby the output at said impacting member may be substantially raised due to resonance while limiting the amplitude of the vibration of said vibrating body to a value close to zero, and a second pneumatic spring between said vibrating member and said base, said second pneumatic spring having a variable spring constant.

References Cited UNITED STATES PATENTS 2,353,492 7/1944 OConnor 259-1 2,636,719 4/1953 OConnor 9448 X 3,089,582 5/1963 Musschoot et al. 7461 X 3,253,701 5/1966 Evans 74-61 X 3,338,384 8/1967 Carrier 7461 X ROBERT E. PULP-REY, Primary Examiner ALAN E. KOPECKI, Assistant Examiner U.S. c1. X.R. 

